[syslinux] PXELINUX based kickstart query (probably OT)

[Geert Stappers]

Op 16-10-2006 om 08:08 schreef H. Peter Anvin:
> Coe, Colin C. (Unix Engineer) wrote:
> > Hey all
> > 
> > I tried 'dd if=/dev/zero of=/dev/sda bs=2 seek=255 count=1' and while a
> > network boot was forced, all the partition info on /dev/sda was lost.  
> 
> The partition info is not lost, but the OS or partitioning software may 
                                                                      ^^^
> not recognize the partitioning table without the boot signature (which 
> is bad design, but somewhat hard to avoid since there isn't a decent 
> magic number anywhere in the DOS partition table.)

So it _may_ work in other situations.

> > I tried 'dd if=/dev/zero of=/dev/sda bs=446 count=1' and after POST the
> > workstation just sits a blank screen when it should have either gone to
> > a PXE screen or GRUB.  On the bright side, the partition ifo was intact
> > so fixing it was easy.
> > 
> > So I just need a combination of these to outcomes  :)
> > 
> > Any ideas?
> 
> Nope, you're screwed.

What about replacing the bootsector's executable code with

     LD  AX,boot_failed_code ; assume AX holds return value
     RTS

or something other that returns and allows a network boot?

Once the contents is known, you can do

  dd if=nextboot of=/dev/sda


Anyway: 
Please update http://syslinux.zytor.com/wiki/index.php/BootsectorIBMPC#Disable_booting



Cheers
Geert Stappers